Primary EBV infection results in a slight increase in effector memory RA⁺, but not CD27⁻RA⁺, CD8⁺ T cells. PBMCs from each subject were stained with antibodies against CD3, CD4, CD8, CD11a, CD45RA, CCR7, CD62L, and CD27. All panels show analysis of CD3⁺CD8⁺ T cells. (A) Memory phenotype CD8⁺ T cells were defined as CD11a^hi. The percentage of cells in this gate was analyzed in 14 subjects before (Pre-IM) or at least 350 d after primary EBV infection (Post-IM). The mean day after infection was 750 (the p-value was determined using a paired Student’s t test). (B) CCR7 and CD45RA expression was examined on CD8⁺ T cells from subjects before or at least 350 d after primary EBV infection. Central memory (CM), effector memory (EM), and effector memory RA (EMRA) subsets were defined as shown. Statistically significant changes are indicated with an asterisk (paired Student’s t test: *, P < 0.05). Error bars indicate standard deviation. (C) CD27 and CD45RA expression was examined on CD8⁺ T cells in 16 subjects. Eight of these were CMV seropositive at enrollment, and the other eight were CMV seronegative and remained negative during the duration of the study. Scatter plot compares the percentage of CD27 negative, CD45RA⁺ (CD27⁻RA) CD8⁺ T cells in CMV seropositive or seronegative individuals (n = 8/group; unpaired Student’s t test, significant). The bar graph shows the mean and standard deviation of CD27⁻RA CD8⁺ T cells before versus after primary EBV infection (n = 6/group; paired Student’s t test, not significant for either). (A and C) Horizontal bars indicate the mean.